The closing of body passages by means of members which can swell has previously been proposed. Such closing of passages and cavities in human or animal bodies may be justified for contraceptive reasons, in which case the oviducts or testicular ducts are closed, or for reasons of illness which require a blocking of a body passage.
The expansible member in question was previously made of fibrous substances which swell on absorbing body fluid, but later it was found that suitable materials are certain water-absorbing copolymerized plastics, so-called hydrogels. The closing is effected in that the expansible member is inserted in the unswollen state in the body passage in question. The shape and dimensions of the member are adapted so that it can easily be introduced into the passage. After introduction, it absorbs fluid from the surrounding tissues and swells. By this means, the passage is blocked as intended while at the same time the member obtains a firm hold therein. Nevertheless, the material should be substantially inert with respect to the body fluid and the surrounding tissues so that the member is retained intact and can be removed when it has served its purpose. As a result, the functioning of oviducts or testicular ducts can be restored, for example, after being blocked with a preventive aim.